For home networking of devices, various home network standards have become available in the meantime. The bus standard IEEE 1394, in particular, has become established in the art of entertainment electronics. Said standard enables communication between the entertainment electronics devices at a very high data rate. Data rates of 100, 200 and 400 Mbit/s are supported (even higher data rates will be supported in the future). This is enough to transmit both asynchronous data packets for controlling the network stations and isochronous audio and video data streams in parallel. However, the IEEE 1394 standard only specifies the lower layers of the ISO/OSI reference model for data communication, namely the physical layer, the data link layer and parts of the network layer. The higher layers, namely the transport layer, session layer, presentation layer and application layer, are unspecified, however.
A consortium of entertainment electronics companies has undertaken also to define the higher layers for data interchange between the entertainment electronics devices. This standard is known under the abbreviation HAVi, where HAVi stands for Home Audio/Video interoperability. This standard specifies a so-called interoperability middleware, which ensures that products from different manufacturers mutually understand one another, i.e. cooperate in order to jointly fulfill tasks via the network.
A different consortium of companies, in particular companies from the computer industry, headed by Microsoft, has started a different initiative for specifying a network control software based on the existing Internet Protocol (IP). This network system has become known under the abbreviation UPnP (Universal Plug and Play). In the case of this system, the specification is not primarily effected for entertainment electronics devices, rather other devices may also be integrated in the network, such as, in particular, personal computers, domestic appliances of white goods, such as refrigerators, microwave ovens, washing machines, and heating controllers, lighting controllers, alarm systems, etc.
Although the two home network standards HAVi and UPnP are sometimes regarded as competitors, they are nonetheless used at least in part for a different purpose, and a scenario is foreseen in which both networks exist alongside one another in a household, said networks being connected to one another via a gateway, however. It shall then become possible to control the devices in the UPnP network from the HAVi network, and vice versa. The connection unit between the two networks is referred to as “gateway” hereinafter. The term gateway is often differentiated from the term “bridge” that is likewise customary otherwise. The difference between a bridge and a gateway is seen in the fact that a bridge transfers the data packets on the data link layer to the respective other network, whereas in a gateway the data packets are already transferred on a higher layer in the ISO/OSI reference model.
Previous work on gateways for the connection of HAVi and UPnP networks has always been based on a so-called “proxy-based gateway” approach. This involves the following: in order that the UPnP network stations are visible from an HAVi device, the UPnP devices are represented on the HAVi side in the gateway by so-called HAVi-DCM code units. In this case, DCM stands for Device Control Module and forms an interface for controlling the general functions of a device. These additional DCMs are then logged on in the HAVi network and can be addressed from the HAVi devices. In this case, a DCM code unit is necessary for each UPnP network station. If the network station offers different functionalities, such as e.g. a customary television set having the functionality of a tuner, an amplifier and also a display device, then, in addition to the DCM, a number of so-called FCMs are provided, if appropriate, in a DCM code unit. In this case, an FCM is a so-called Functional Component Module which is thus used to cover an interface for controlling a specific device functionality.
Conversely, the HAVi network stations are also intended to be addressed from the UPnP side. On the UPnP side, an HAVi device is represented by a so-called UPnP device. Therefore, a corresponding UPnP device is also kept ready in the gateway for each HAVi network station. A so-called XML device description exists for each UPnP device. In this case, XML stands for the description language Extension Markup Language. The counterpart for an HAVi FCM on the UPnP side is a so-called “service”. Therefore, a plurality of UPnP services may be described in a UPnP device. The conversion between HAVi DCM/FCM and UPnP devices/services is intended to be effected as completely as possible.